Something that's been puzzling me for quite a while is the way the RV-12 engine mount is connected to the firewall. Engine mounts on other RV's, Cessna's and most other aircraft I've seen, typically connect at the outer edges of the firewall in line with main horizontal fuselage structural members. However on the 12, the two upper braces are simply bolted to a pair of welded brackets riveted to the upper firewall and the instrument bay shelf, which in turn acts as a horizontal diaphragm to take the loads back to the upper fuselage stringers. This seems like a somewhat flimsy arrangement, although more than 330 flying aircraft suggests that it works OK.
I have thought about adding some angle braces to the underside of the shelf to stiffen it against buckling and transfer load if the engine tried to force its way back into the cockpit in a head-on impact. However, I'm hesitating because I haven't been able to decide if this attachment method is part of a clever progressive crumple design that would be compromised if I tried to stiffen it. Consequently, rather than try to second guess what Vans had in mind I'll probably follow the`if it's not broke, don't fix it' principle, but I'm just curious as to why the -12's mount should be different to the other RV's. Does anybody know?
I have thought about adding some angle braces to the underside of the shelf to stiffen it against buckling and transfer load if the engine tried to force its way back into the cockpit in a head-on impact. However, I'm hesitating because I haven't been able to decide if this attachment method is part of a clever progressive crumple design that would be compromised if I tried to stiffen it. Consequently, rather than try to second guess what Vans had in mind I'll probably follow the`if it's not broke, don't fix it' principle, but I'm just curious as to why the -12's mount should be different to the other RV's. Does anybody know?
Last edited:
